This invention relates generally to a plastic sheet capable of being shaped by a cold tool into a product by interposing and compressing the sheet between two mold parts. More specifically, this invention relates to a semi-rigid thermoformable foam with infrared receptors and to the method of shaping a sheet of such foam after heating the same to its thermoforming softening temperature.
For some time, sheets of semi-rigid thermoformable sheets of polyurethane foam has been used for core material on various types of products such as headliners and visors utilized in automotive vehicles. The foam is processed in a slab form and slit into sheets by the plastic supplier. The foam is then heated to its thermoforming temperature prior to forming it to shape in a cold tool, generally at room temperature for forming the products. The semi-rigid polyurethane foam has a thermoforming temperature range at which it is necessary to heat the sheet prior to placing the sheet between the mold parts of the forming tool. It is desired that the foam exhibit desired processing properties of fast heating, uniform temperature distribution, and slow cooling. Heretofore, the polyurethane foam utilized has exhibited the desired properties of uniform temperature distribution and slow cooling. However, the time required to heat both the surfaces and core of the sheets of polyurethane foam has been undesirable because of the time consumed in such heating, making it inefficient and thus costly to shape the foam into the desired product. Therefore, this time problem has created the necessity for some way to decrease the heating time of the polyurethane foam sheet.